Library Philosophy and
Practice 2012

Stem Cell Research: A Bibliometric Analysis from 1999-2008

Introduction

Stem cell research is a vital area of study. It is of interest to scientists in India and all countries [1]. Bibliometrics is a truly interdisciplinary research field. Bibliometrics comprises mathematics, social science, natural sciences, engineering, and life sciences. Bibliometric studies such as a work on the research productivity in ophthalmic and vision research used both the number of publications and qualitative measures of journals.[2] This article is a bibliometric study of a part of the literature on stem cell research.

Bibliometrics

The terms bibliometrics and scientometrics were introduced by Pritchard and by Nalimov and Mulchenko in 1969. Pritchard explained the term bibliometrics as "the application of mathematical and statistical methods to books and other media of communication." There have been many bibliometric studies of the literature in the sciences in the last 40 years. In chemical information and computer sciences (CICS), a bibliometric approach was used to survey state-of-the-art of research. Journal of Chemical Information and Computer Sciences (JCICS) has been the leading journal in this area for the last 30 years. [3] One important element of bibliometrics is the author co-citation frequency matrix. It has been used to study Knowledge Management. Author co-citation frequencies were derived from the 1994-1998 academic literature and captured by the single search phrase of "Knowledge Management." [4] An economically and scientifically developing country like China has done research in the field of Neuroscience. A MEDLINE-based bibliometric analysis was done of the Chinese output in neuroscience for 1984 to 2001. [5] Research was done from the Inorganic Crystal Structure Database with the focus on growth rate, distribution of publications, productivity of authors, and multiple authorship patterns. [6] HIV/AIDS Research in India revealed the rapid growth of literature from 1992 onwards. The authorship distribution was examined using Lotka's Law. To identify the core journals Bradford's Law was used. The relative productivity of India was low and the focus was more on research and development. [7] Various aspects of nutrition research in Bangaladesh from 1972 to 2006 has been analyzed using bibliometrics. [8]

Materials and Methods

This study was confined to the published literature on the sub-discipline “Stem Cell” from the MEDLINE database. MEDLINE is the National Library of Medicine's (NLM) leading bibliographic database, which contains more than 18 million references to journal articles in the life sciences with a concentration on biomedicine. MEDLINE covers biomedicine, health, life sciences, biology, environmental science, marine biology, plant, and animal science. The period chosen for the study was 1999 to 2008. The total number of records was 54,373.

Need for the Study

A stem cell is a cell that has the ability to divide (self-replicate) for unlimited periods, often throughout the life of the organism. Under the right conditions, stem cells can differentiate to the many different cell types that make up the organism. Many different studies have explored the efficacy of stem cell treatment. [9] [10] [11] [12 [13]

Limitations

The study is confined to literature from 1999 to 2008 that is covered in MEDLINE.

Methods

The MEDLINE database was searched using the the Medical Subject Heading (MeSH) "Stem cell research". This yielded ten years of records that were downloaded into separate text files.

Data Analysis

The data was investigated with Bibexcel. This was developed by Olle Persson of Umeå University in Sweden. This software is designed to analyse bibliographic data..

Objectives of the Study

Observe authorship patterns

Discover the degree of collabration

Measure the quantum of research productivity in MEDLINE

Study the linguistic distribution

Study the geographical distribution

Study the growth rate of production of literature

Identify the most frequent journals

The yearwise distribution of data according to the number of authors is presented in Table 1. The table shows that nearly 12.6% of the contributors were only by single authors and 12.86% is two authors research output. It clearly collaboration in stem cell research.

Table 1. Authorship pattern in Stem Cells

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Total

%

Single Authors

328

434

676

708

604

759

875

896

768

808

6856

12.6

Two Authors

331

416

463

590

620

706

843

868

973

1180

6990

12.86

Three Authors

344

393

435

485

541

619

739

820

912

942

6230

11.46

Four Authors

394

398

439

487

530

594

651

708

914

885

6000

11.03

Five Authors

371

395

411

495

502

543

622

785

860

894

5878

10.81

Six Authors

364

341

376

399

471

546

621

795

842

861

5616

10.33

Seven Authors

252

269

291

293

357

429

486

589

642

699

4307

7.92

Eight Authors

217

220

218

251

254

320

409

450

533

609

3481

6.4

Nine Authors

126

161

156

164

227

258

286

354

383

476

2591

4.77

Ten Authors

87

91

110

135

168

202

220

298

302

366

1979

3.65

More than Ten Authors

224

235

240

296

327

392

507

631

741

852

4445

8.17

Total

3038

3353

3815

4303

4601

5368

6259

7194

7870

8572

54373

100

Diagram 1 depicts the authorship pattern in stem cell research from 1999 to 2008. Five or more authors are found on 41.24% of the records.

Diagram 1. Degree of Collaboration

The extent of the degree of collaboration was measured with the formula devised by K. Subramaniam.

The formula is

C = Nm / Nm + Ns

Where

C = Degree of Collaboration in a discipline

Nm = Number of multiple authored papers

Ns = Number of single authored papers

Accordingly, the Degree of Collaboration has been calculated for the year 1999 is as follows:

2710 2710

C = -------------- = ------- = 0.89

2710 + 328 3038

The yearwise degree of collaboration falls between 0.82 and 0.9. The degree of collaboration for any subject ranges from 0.01 to 0.99 and it is always below 1 which has been proved by Karisiddappa, Maheswarappa and Shirolin Psychology and Bandyopadhyay in different disciplines such as Mathematics, Physics, Philosophy, Political Science and Mechanical Engineering.

Table 2. Degree of Collaboration in Stem Cell Research

Years

Single

Two

Three

Four`

Five

Six

Seven

Eight

Nine

Ten

More than Ten

Total

More than One Authors

Degree of Collaboration

1999

328

331

344

394

371

364

252

217

126

87

224

3038

2710

0.89

2000

434

416

393

398

395

341

269

220

161

91

235

3353

2919

0.87

2001

676

463

435

439

411

376

291

218

156

110

240

3815

3139

0.82

2002

708

590

485

487

495

399

293

251

164

135

296

4303

3595

0.83

2003

604

620

541

530

502

471

357

254

227

168

327

4601

3997

0.87

2004

759

706

619

594

543

546

429

320

258

202

392

5368

4609

0.86

2005

875

843

739

651

622

621

486

409

286

220

507

6259

5384

0.86

2006

896

868

820

708

785

795

589

450

354

298

631

7194

6298

0.87

2007

768

973

912

914

860

842

642

533

383

302

741

7870

7102

0.9

2008

808

1180

942

885

894

861

699

609

476

366

852

8572

7764

0.9

Total

6856

6990

6230

6000

5878

5616

4307

3481

2591

1979

4445

54373

47517

0.87

Quantum of Stem Cell Research Activity

The research productivity in the source database and the quantum of records on stem cells covered is shown in the Table 3. Only 0.95% of the records in the MEDLINE database are on stem cells. The yearwise distribution of stem cell literature is shown in this table.

Table 3. Percentage of Literature Published from 1999 to 2008 in Stem Cell Research

Years

Total No. of Records

Records on Stem Cell

Percentage

1999

462148

3038

0.66

2000

489198

3353

0.69

2001

508109

3815

0.75

2002

523264

4303

0.82

2003

549977

4601

0.84

2004

579750

5368

0.93

2005

613406

6259

1.02

2006

637129

7194

1.13

2007

660193

7870

1.19

2008

676822

8572

1.27

Total

56,99,996

54373

0.95

Quantum of Stem Cell Research Productivity

The research productivity on 'Stem Cell' covered in the database is shown in Table 4.

Table 4. Quantum of Literature Published on Stem Cell from 1999 to 2008

Years

Records on Stem Cell

Percentage

Cumulative Percentage

1999

3038

5.58

2000

3353

6.17

11.75

2001

3815

7.02

18.77

2002

4303

7.91

26.68

2003

4601

8.46

36.14

2004

5368

9.88

45.02

2005

6259

11.51

56.53

2006

7194

13.23

68.76

2007

7870

14.47

84.23

2008

8572

15.77

100

Total

54373

100

The yearwise distribution of literature is shown in Table 4. The highest number of records (8,572) was published during 2008, followed by 7,870 in 2007, and 7,194 in 2006.

Distribution of Research Production by Language vs Year

The distribution of literature by language is presented in Table 5.

Table 5. Stem Cell Research Productivity by Language

S.No.

Languages

1999

2000

01

02

03

04

05

06

07

08

Total

%

1

English

2671

2901

3208

3758

3925

4785

5583

6507

7135

7655

48128

88.52

2

Japanese

40

40

31

38

58

49

59

59

55

80

509

0.94

3

Chinese

39

40

47

98

141

182

255

239

273

240

1554

2.86

4

Russian

25

8

29

20

36

29

38

30

45

46

306

0.56

5

French

23

27

31

19

45

33

46

37

81

48

390

0.72

6

Spanish

14

12

17

17

15

13

13

16

23

18

158

0.3

7

German

7

22

20

37

28

34

23

36

33

37

277

0.52

8

Polish

6

5

3

6

12

11

10

11

15

15

94

0.18

9

Czech

3

6

9

6

10

7

2

3

11

12

69

0.14

10

Italian

3

4

8

7

8

3

7

5

8

10

63

0.13

10

Norwegian

2

3

5

2

7

3

2

2

7

9

42

0.09

11

Other

155

285

407

295

316

219

221

249

184

402

2733

5.04

16

3038

3353

3815

4303

4601

5368

6259

7194

7870

8572

54373

100

Distribution of Stem Cell Research Productivity - Country Vs Year

Stem cell research by country and yearwise is presented in the Table 6. The USA has ranks first followed by the United Kingdom 11,397, and the Netherlands with 2,942 records. India is in 16th place with 203 records.

Table 6. Year vs. Country wise Distribution of Stem Cell Research

S

No

Country

1999

2000

01

02

03

04

05

06

07

08

Total

%

1

United-States

1597

1714

2015

2284

2503

2902

3446

3874

4122

4513

28970

53.28

2

England

675

743

773

888

916

1103

1213

1509

1670

1907

11397

20.96

3

Netherlands

183

198

209

262

237

263

344

339

441

466

2942

5.41

4

China

48

44

61

116

177

234

315

312

384

342

2033

3.74

5

Germany

71

121

145

124

113

151

174

223

211

284

1617

2.97

6

Japan

59

69

70

71

101

100

128

130

146

176

1050

1.93

7

Switzerland

70

106

92

85

50

74

59

111

101

127

875

1.61

8

Ireland

30

52

81

81

57

57

64

55

99

98

674

1.24

9

France

53

49

60

62

66

78

69

80

98

81

696

1.28

10

Italy

61

45

58

51

56

55

66

88

68

68

616

1.13

11

Denmark

39

50

47

47

44

58

61

74

61

64

545

1

12

Scotland

6

16

19

26

14

15

26

40

52

53

267

0.49

13

Spain

19

7

21

31

24

47

36

35

41

45

306

0.56

14

Russia

20

8

30

23

37

32

31

27

44

44

296

0.55

15

Australia

7

8

13

16

22

14

24

24

37

38

203

0.38

16

India

4

6

3

5

10

8

6

14

9

6

71

0.13

17

Others

96

117

118

131

174

177

197

259

286

260

1815

3.34

18

Total

3038

3353

3815

4303

4601

5368

6259

7194

7870

8572

54373

100

Relative Growth Rate and Doubling Time for Stem Cell Research Output

The Relative Growth Rate (RGR) is the increase in number of articles/pages per unit of time. The mean Relative Growth Rate (R) over the specific period of interval can be calculated from the following equation:

Loge 2W – loge 1W

1-2`R =

2T - 1 T

Whereas

1-2`R = mean relative growth rate over the specific period of interval

loge1W = log of initial number of articles/pages

loge 2W = log of final number of articles/pages after a specific period of interval

2T - 1T = the unit difference between the initial time and the final time

The year can be taken here as the unit of time. The RGR for both articles and pages can be calculated separately.

Therefore

1 - 2R(aa -1 year -1) can represent the mean relative growth rate per unit of articles per unit of year over a specific period of interval.

and

1 - 2 R ( pp -1 year -1) can represent the mean relative growth rate per unit of pages per unit of year over a specific period of interval.

It is seen from rable that there is decrease in RGR by year.

Table 7. RGR and Dt for Stem Cell Research Output by Year-wise

Year

Quantum of Output

Cumulative Total of Output

W1

W2

RGR

Dt(a)

1999

3038

3038

8.018955

2000

3353

6391

8.018955

8.762646

0.743691

0.931838

2001

3815

10206

8.762646

9.230731

0.468085

1.4805

2002

4303

14509

9.230731

9.582524

0.351793

1.969906

2003

4601

19110

9.582524

9.857967

0.275443

2.515951

2004

5368

24478

9.857967

10.10553

0.247563

2.799287

2005

6259

30737

10.10553

10.33322

0.227692

3.04358

2006

7194

37931

10.33322

10.54352

0.210302

3.295268

2007

7870

45801

10.54352

10.73206

0.188537

3.675667

2008

8572

54373

10.73206

10.90362

0.171562

4.039361

The RGR has decreased from 2000 (0.74) to 2008 (0.17) in the span of 10 years (Figure 1).The Doubling Time (Dt) has increased when calculated yearwise.The Doubling Time increases from 0.93 in 1999 to 4.03 in 2008 (Figure 2).

Figure 1

Doubling Time (Dt)

There exists a direct equivalence between the relative growth rate and the doubling time [17]. If the number of articles/pages of a subject doubles during a given period then the difference between the logarithms of numbers at the beginning and end of this period must be logarithms of number 2. If natural logarithm is used this difference has a value of 0.693. Thus the corresponding doubling time for each specific period of interval and for both articles and pages can be calculated by the formula:

The Table 8 reveals that the distribution of the stem cell research output according to publication type and year of publication.

It is an accepted fact that most of the scholarly communication of scientific research is published in journals and sometimes presented in the conferences. Of course, those conference papers are further updated and published in journals of the respective field of knowledge. Therefore, scientific communication is being mostly made through periodicals, the primary vehicles of research communication.

In this study, about 75.27% have published in journals, 7.45% have published in comparative studies, and 2.47% are published in comments.

Table 8. Publication Type of Stem Cells Vs Year

Publication Type

1999

2000

01

02

03

04

05

06

07

08

Total

%

Case Reports

39

95

89

99

89

84

60

92

83

67

797

1.47

Clinical Trial

109

101

79

74

93

54

78

84

101

50

823

1.51

Comment

33

75

69

101

114

138

172

183

205

254

1344

2.47

Comparative Study

216

232

302

301

407

516

602

616

474

385

4051

7.45

Journal Article

2341

2535

2749

3247

3335

3887

4508

5330

6101

6895

40928

75.27

Letters

25

24

28

21

20

40

40

42

59

56

355

0.65

Others

275

291

499

460

543

649

799

847

847

865

6075

11.18

Total

3038

3353

3815

4303

4601

5368

6259

7194

7870

8572

54373

100

Figure 3

Figure 3 represents the different types of publications in the research output in Stem Cells.

Ranking of Journals in Stem Cell Research

Ranking of the journals on the research output on 'Stem Cell "during the study period has been presented in the below Table 9. With the 1908 contributions "Blood" Journal took in the First Rank, the "Stem-Cells" with 971 contributions and "Proc-Natl-Acad-Sci-U-S-A." 890 contributions stand Second and Third Rank. The researcher finds out of 15 ranking journals for the specific publication. Bone Marrow Transplantation goes to sixth place.

Table 9. Ranking of Journals in Stem Cell Research

Name of the Journal

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Total

Rank

Blood.

202

212

178

223

214

188

190

167

178

156

1908

1

Stem-Cells.

48

32

65

68

76

77

82

313

95

115

971

2

Proc-Natl-Acad-Sci-U-S-A.

79

56

52

79

89

70

101

121

124

119

890

3

Bone-Marrow-Transplant.

104

88

79

106

73

72

85

81

89

67

844

4

J-Immunol.

90

76

82

71

79

60

61

66

44

51

680

5

Bone-Marrow-Transplant.

110

94

73

51

79

48

54

41

42

67

659

6

Development.

55

72

67

61

39

65

60

67

72

80

638

7

Science.

47

54

69

66

47

65

77

67

81

56

629

8

Nature.

28

46

5

51

55

76

80

96

84

102

623

9

J-Biol-Chem.

31

33

42

47

45

87

71

61

56

61

534

10

Dev-Biol.

31

29

36

26

36

43

54

75

81

65

476

11

Leukemia.

66

42

31

56

37

26

29

34

59

34

414

12

Br-J-Haematol.

60

76

54

55

46

32

14

23

21

26

407

13

Ann-N-Y-Acad-Sci.

39

8

36

15

34

20

63

23

43

11

292

14

Haematologica.

47

32

16

22

31

24

31

34

29

22

288

15

Distribution of Journals in Stem Cells based on Bradford Law of Scattering

Bradford first formulated his law, but it did not receive wide attention until the first publication of his book 'Documentation' in 1948. Bradford examined all of the journal titles contributing to a bibliography on applied Geophysics. He divided the list into three 'zones' each containing roughly equal number of references. On the basis of this observation Bradford deduced his law.

"If scientific periodicals are arranged in the order of decreasing productivity of articles on a given subject, they may be divided into a nucleus of periodicals more particularly devoted to the subject and several groups or zones containing the same number of articles as the nucleus where the number of periodicals in the nucleus and the succeeding zones will be as 1: n:n2"

Table 10. Distribution by Zone of Cited Journals and References in Stem Cells

Zone

No. of Journals

No. of Papers

No.

(%)

No.

(%)

Zone 1

156

1.46

18156

33.39

Zone 2

1288

12.02

17458

32.10

Zone 3

9269

86.52

18759

34.51

Total

10713

100

54373

100

It is seen from the table 10 shows that 156 core journals are grouped in zone-1 published 18156 articles accounts for one third of the total output. Similarly the second zone comprises of 1288 journals and 9269 journals grouped in third zone. The Bradford's Law states that the number of periodicals in zones, the first zone and second zones will be 1: n: n2...... According to the relationship is the zone will be 156: 1288: 9269. On comparison with the data in Table, it is clear that the trend of research publication confirms the implication of Bradford's Law

Findings

1. A total of 54,373 publications were covered in MEDLINE database for the period 1999-2008.

2. USA ranks as the top most country with maximum number of contributions followed by United Kingdom England and Netherland as second and third positions respectively..

3. It was found that about 88.52% of total output was published in English language, followed by Chinese 2.86% and Japanese 0.94%

4. "Journal articles" contributed 75.27% followed by "Comparative Study" 7.45% of the total output.

5. There was a decrease in Relative Growth Rate and an increase in the Doubling Time for research productivity from year after year throughout the study period.

6. The degree of collaboration has been arrived at 0.9 during the study period

7. It was found that a maximum number of contributions (1908) were published in the journal 'Blood.. This is followed by 'Stem Cell' with 971 contributions

8. The research productivity of Stem Cell confirms the implications of Bradford's Law of Scattering

9. There exists a significant level of difference between Stem Cell research performance of Indian scientists and scientists of other countries.

Conclusion

Research in stem cells will help us understand how they transform into the dazzling array of specialized cells that make us what we are. A better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause of medical deffects. Another imprtant application of stem cells is making cells and tissues for medical therapies. Today, donated organs and tissues are often used to replace the diseased or destroyedn organs. Unfortunately, a large number of people needing a transplant far exceeds the number of organs available for transplantation. Stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a myriad of diseases, conditions, and disabilities including Parkinson's disease, amyotrophic lateral sclerosis, spinal cord injury, burns, heart disease, diabetes, and arthritis. Research with the use of stem cells in the treatment of diseases like heart, liver, brain and spinal cord had remained in the experimental stage like India. Limited contolled clinical trials in human had been permitted. The results were closely monitored by experts. [14] India started to set up a "stem cell priority fund" to maintain research via stem cells and find healing for diabetes, heart and nerve diseases. ''We have submitted a proposal of an exclusive fund for stem cell research. I think the government is keen to set up the stem cell priority fund,'' announced D Balasubramanian, Chairman of the task force on stem ccell research of the Department of Biotechnology (DBT), at the Indo-UK stem cell workshop organised jointly by India and Britain.